Synthesis of Eu3+-activated BiOF and BiOBr phosphors: photoluminescence, Judd–Ofelt analysis and photocatalytic properties

Abstract

A series of Bi_1−xEu_xOX (X = F and Br; x = 0, 0.01, 0.03 and 0.05) phosphors were synthesized at relatively low temperature and short duration (500 °C, 1 h). Rietveld refinement results verified that all the compounds were crystallized in the tetragonal structure with space group P4/nmm (no. 129). Photoluminescence spectra exhibit characteristic luminescence ⁵D₀ → ⁷F_J (J = 0–4) intra-4f shell Eu³⁺ ion transitions. The magnetic dipole (⁵D₀ → ⁷F₁) transition dominates the emission of BiOF:Eu³⁺, while the electric dipole (⁵D₀ → ⁷F₂) peak was stronger in BiOBr:Eu³⁺ phosphors. The evaluated CIE color coordinates for Bi_0.95Eu_0.05OBr (0.632, 0.358) are close to the commercial Y₂O₃:Eu³⁺ (0.645, 0.347) and Y₂O₂S:Eu³⁺ (0.647, 0.343) red phosphors. Intensity parameters (Ω₂, Ω₄) and various radiative properties such as transition rates (A), branching ratios (β), stimulated emission cross-section (σ_e), gain bandwidth (σ_e × Δλ_eff) and optical gain (σ_e × τ) were calculated using the Judd–Ofelt theory. It was observed that BiOBr:Eu³⁺ phosphors have a long lifetime (τ) and better optical gain (σ_e × τ) as compared to reported Eu³⁺ doped materials. Furthermore, these compounds exhibit excellent photocatalytic activity for the degradation of rhodamine B dye under visible light irradiation. The determined radiative properties and photocatalytic results revealed that BiOBr:Eu³⁺ phosphors have potential applications in energy and environmental remedies, such as to develop red phosphors for white light-emitting diodes, red lasers and to remove toxic organic industrial effluents.